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08 Apr 2018
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TOPIC: Twilight altitude setting

Twilight altitude setting 2 weeks 6 days ago #25864

I'm wondering if there can't be a user defined setting where if the sun is below a threshold altitude, the time is considered past twilight. I know this is an odd request, but standard astronomical dusk requires the sun to be below 18 degrees from below the horizon. Some locations for imaging have skies brighter than true dark sites, so the sky gets as dark as it can well before the sun gets to -18 degrees. This is also the case w/ the moon up.

Also, you can cheat a bit and image in narrowband filters before the sun gets to -18 degrees. This adds up and allows for a bit more imaging time.

Gabe

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Re:Twilight altitude setting 1 week 6 days ago #25996

Noted, this should be relatively easy to insert, the altitude of the Sun at a given time can be calculated. This would essentially add a spinbox in the UI, with default value -18 degrees, and involve the same algorithm as target scheduling.

-Eric

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Re:Twilight altitude setting 1 week 6 days ago #25997

  • jpaana
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This would be very useful here in the north where at the moment we don't have astronomical darkness at all :) Also in some cases it might be useful to be able to start the job asap in the evening but still have twilight as abort condition in the morning.

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Re:Twilight altitude setting 1 week 6 days ago #25998

@jpaana You mean having dawn and dusk spinboxes instead of twilight alone?

-Eric

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Re:Twilight altitude setting 1 week 6 days ago #26000

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Yes, or just setting to select if the limit applies to one or both.

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Re:Twilight altitude setting 1 week 6 days ago #26002

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So this would mean that you start imaging quite early after sunset and it will stop as soon as the Sun passes through the meridian (to the north below that horizon) because that’s when dusk ends and dawn starts, doesn’t it? That would mean a waste of some dark enough hours. Perhaps a setting specifying how long after sunset and before sunrise imaging should start and stop, repectively, would be better?

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Re:Twilight altitude setting 1 week 6 days ago #26004

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No, not meridian, I mean specifying if the limit should apply both when starting (dusk) or ending (dawn) or both, currently it's always both, so the sequence doesn't start until it's dark enough. My use case would be that I want to start the sequence (usually repeating) asap when I'm setting things up and it might still not be astronomical dark, but then I'd like it to stop at - 6 degrees for example (civil dawn I think). Currently I have turned twilight check off and specified end time manually, but that was a bit cumbersone when the day shortened by 20 minutes each day around equinox :) Also specifying time isn't as useful in some cases as the degree as duration of dusk/dawn varies. But it might be a good option as it's possibly easier to understand than how low sun must be.

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Re:Twilight altitude setting 1 week 6 days ago #26006

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Yes that makes sense. I was merely wondering about the wording of the solution :side:

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Modded Canon EOS 700D with a WO ZS 71 ED on a SW HEQ5-Pro

Re:Twilight altitude setting 1 week 6 days ago #26009

jpaana wrote: This would be very useful here in the north where at the moment we don't have astronomical darkness at all :) Also in some cases it might be useful to be able to start the job asap in the evening but still have twilight as abort condition in the morning.


I concur. At least there should be a choice in the scheduler to start and stop imaging at nautical twilight (i.e. -12 deg) and/or at astronomical darkness. For much of Northern Europe, the twilight setting would have no meaning otherwise for much of summer.

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Re:Twilight altitude setting 1 week 6 days ago #26011

So, two altitude settings, one for dusk as a start boundary, one for dawn as a stop boundary? And tooltip to remind what is astronomical, nautical and civil twilight.

Altitude/time relation can be determined by adjusting kstars time and while looking at the location of the Sun I suppose.

One need for fixed twilight time could be public lights turning off or on though. In my village this happens at a fixed schedule throughout the year, local time.

Probably no need to offer a lock between the two settings (like picture scaling ratio in image editors).

This wishlist item can be extended to management of dawn/dusk calibration frames. That would add a dawn/dusk interval setting where lights must not be taken, but calibration frames can.


-Eric

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